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  Morphology control of substituted diacetylenic monomers for shelf life monitoring systemsUSPTO Application #: 20060025647Title: Morphology control of substituted diacetylenic monomers for shelf life monitoring systems Abstract: A system for recovering a diacetylenic monomer shelf life monitoring compound of reduced particle size and narrow size distribution range which comprises quenching a solution of the monomer by mixing the solution in a lower temperature quenching fluid having a base temperature which is at least about 30° C. below the nominal temperature at which the monomer compound recrystallizes from solution, the mixing being effected in such a manner as to limit the resulting quenching mixture temperature to one which is not higher than a maximum of about 15° C. above the quenching fluid base temperature. (end of abstract) Agent: Senior Vice President, Operations Temptime Corporation - Morris Plains, NJ, US Inventors: Thaddeus Prusik, Dawn E. Smith, Ingo H. Leubner, Wesley A. Olmsted USPTO Applicaton #: 20060025647 - Class: 585812000 (USPTO) Related Patent Categories: Chemistry Of Hydrocarbon Compounds, Purification, Separation, Or Recovery, By Cooling Of Liquid To Obtain Solid, E.g., Crystallization, Etc. The Patent Description & Claims data below is from USPTO Patent Application 20060025647. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present invention relates to systems, and elements, components, and compositions therefor, comprising substituted diacetylenic monomer components which are useful in monitoring and indicating the elapse of a predetermined integral of deleterious ambient conditions, such as time, temperature, humidity, actinic radiation, vaporous atmosphere, and the like, to which an associated product has been exposed and which thereby establish the shelf life of such a product. In particular, the invention provides means for economically preparing such monomer components as highly active, reduced-size particles which exhibit remarkable consistency over a narrow range of size distribution. [0002] Typically, in monitoring the useful shelf life, i.e., the span of safe or potent utility, of a product of foodstuff, medicament, or the like which is known to be affected by, for example, a thermal ambient, an indicator system, often in the form of an affixed label, is associated with the product and exhibits a readily discernible property variation, such as a change of color or color density, at the end of the product's shelf life. To this end, such a system may comprise a thermally reactive composition appropriately formulated to provide such a color change response substantially concurrently with elapse of a given time-temperature integral commensurate with expiration of the product's predesignated shelf life. Of particular utility in such responsive compositions of shelf life monitoring systems are substituted diacetylenic monomer components which exhibit a distinct color change as a result of and generally concomitant with a solid state polymerization effected by changes in ambient conditions; for example, as in the case of a time-temperature indicator (TTI) system, an integral of time and temperature. [0003] The distinct responses, e.g., color changes, of diacetylenic monomer components to thermal and other environmental stimuli provide bases for numerous highly functional and reliable monitoring system embodiments. One widely utilized type of such a system is implemented by incorporating a selected reactive monomer component into a composition formulated as a printable ink which is applied to a label capable of being associated, by adhesive layer or other means, with a target shelf life-limited product, such as an item of foodstuff or medicament. Selected to react in solid state polymerization to variant temperature ambients over a time period satisfying an integral matching the shelf life of the associated product, the diacetylenic component of an applied TTI label ink composition displays a predesignated color or color density signaling expiration of that shelf life. [0004] Substituted diacetylenic monomers have been studied and utilized in shelf life monitoring systems for a substantial time. For instance, such utility of these numerous active monomers comprising at least two conjugated acetylene groups (--C.ident.C--C.ident.C--) and their unique physico-chemical properties, e.g., responsiveness to persistent temperature excursions by transforming into contrastingly colored solid state polymerization reaction products, have been described by Patel et al. (U.S. Pat. No. 3,999,946). The synthesis of these monomers and their incorporation into TTI and other shelf life indicator compositions are discussed there at length and continue to be useful in implementing embodiments of such systems. Also, the use of these diacetylenic monomer shelf life system components and improvements thereon, including broad ranges of substituents and complexes, and improved methods of monomer synthesis and blending in co-crystallization operations, have been described further by Patel (U.S. Pat. No. 4,189,399 and U.S. Pat. No. 4,384,980) and Preziosi et al. (U.S. Pat. Nos. 4,789,637 and 4,788,151). Such useful descriptions and examples of these diacetylenic monomer components finding application in shelf life monitoring systems to which the present invention relates are incorporated herein by reference. It should be noted that although the term "monomer" is used consistently throughout this specification with respect to the active monitor component materials, dimeric and polymeric component compounds of similar basic structure, as previously described in the cited references, are likewise to be considered included in this description. [0005] As noted in the referenced specifications, numerous diacetylenic monomers may be synthesized to yield TTI components of widely varying reactive temperature ranges and resultant color densities. While such monomer components may generally be relied upon to exhibit reproducible results as indicators of shelf life end points, physical and morphological variables in these components, for example the size of their crystalline particles, often have a profound effect upon their response and performance in TTI and other monitoring applications. In addition, further requirements of crystal size limitation are often imposed by the ultimate utilization of the diacetylenic monomer composition, as in the need for sufficiently fine particles to enable formulation of a free-flowing printing ink. [0006] Means for achieving such proper morphology, e.g., sufficiently small and uniform particle size, for diacetylenic monomer components of shelf life monitoring systems have heretofore been reliant, as described in the referenced art, upon expensive, low-efficiency intermediate operations for grinding or pulverizing these active materials. However, operations of this type not only are uneconomical, but they consistently degrade the monomer materials due to the unavoidable generation of heat, along with uncontrolled size reduction over the entire mass of monomer particles with a resultant excessive range of particle sizes. [0007] There has thus existed for some time a need for a ready, reliable, and cost-effective means for achieving and controlling variation in reduced particle size active diacetylenic monomer components for use in TTI and other exposure integral monitoring systems without severely interrupting the system composition process by imposition of costly and inefficient grinding operations. The present invention obviates the noted shortcomings and disadvantages in the preparation of prior diacetylenic monomer component system products and provides means for readily and economically obtaining such monomer components within narrow ranges of desirably small particle sizes which have been shown to provide exceptionally consistent responsiveness in TTI and other such systems. The invention provides such diacetylenic monomer component products which comprise improved and highly effective shelf life systems while greatly reducing costs and achieving significant savings in time and material resources during system formulation. SUMMARY OF THE INVENTION [0008] For use in the preparation of a desired shelf life monitoring system, for instance a TTI device, a substituted diacetylenic monomer of predetermined time-temperature integral may be synthesized as described in the referenced patent specifications by appropriate selection and balance of various parameters, such as precursor acetylenic condensate constituents or substituted variants thereof, conditions of synthesis, matching of components for co-crystallized compositions, and the like. The resulting compound is then initially recovered from the reactant solution as a crude form of the diacetylenic monomer by common crystallization means, such as evaporation, sublimation, solution cooling, or selective salvation. [0009] The crude crystalline monomer may be retained in that form until processed during formulation of the ultimate TTI composition or it may be purified further by dissolution and recrystallization. Previous means for the latter operation have typically comprised batch cooling of monomer solution from a dissolution temperature of about 90 to 100.degree. C. to a temperature below that sufficient for recrystallization of the monomer compound, either by immersion of the solution vessel in an external bath of coolant or by rapid introduction of the monomer solution directly into a body of quenching fluid exhibiting limited solvency for the monomer, due either to its inherent chemical composition or its low temperature. Diacetylenic monomer treated in either manner is normally recovered, after washing, filtration, and drying, as a crystalline product having a wide range of particle sizes, comprising both individual and agglomerate particles. A significant portion of such recrystallized monomer product has a particle size well in excess of the 10 .mu.m range which is preferred in compounding shelf life monitoring system compositions, such as inks for label devices or the like. [0010] The morphology of the recovered diacetylenic monomer also influences the performance of the incorporating monitor compositions in that the consistency of response exhibited by TTI and other shelf life monitoring systems have been observed to be affected in significant measure by the sizes and size distributions of the incorporated diacetylenic monomer particles. Investigations into the behavior of active component diacetylenic monomers have indicated improved consistency of indicator results when their reduced crystalline particle sizes are constrained within narrow ranges. [0011] In order to prepare an effective TTI ink composition comprising a diacetylenic monomer component obtained in the foregoing manner, it previously has been necessary to subject the composition materials, particularly the monomer, to a comminution operation, typically by milling the ink composition, such as with rollers, balls, or high-speed shearing apparatus. Although size reduction is generally achieved, a wide range of monomer particle size distribution and related instability in TTI composition response continue to be prevalent. Further, a significant disadvantage of milling or grinding operations, i.e., heat generation, has been seen to result in premature color-shift polymerization of many of the diacetylenic monomer materials. [0012] With a goal of achieving a reduction of monomer particle size into the preferred range of about 10 .mu.m without resort to deleterious grinding, investigations resulting in the present invention undertook a variety of procedures for recrystallization of synthesized diacetylenic monomer from heated purification solution. One such procedure providing particularly good results comprised quenching the heated monomer solution by introduction into a low-temperature, miscible quenching fluid in such a manner as to achieve and maintain a rapid temperature decrease of the resulting fluid mixture into a maximum range of preferably about 10 to 15.degree. C. which is at least about 30.degree. C. below the nominal monomer recrystallization temperature, i.e., the temperature at which the monomer normally exhibits significant recrystallization from the solution as a result of moderate external bath cooling. Surprisingly, not only did such rapid cooling result in a decrease of the mean particle size of the recrystallized monomer into a range approaching the preferred 10 .mu.m, but the range of particle size distribution narrowed significantly with resulting improvement in consistency of indicator performance, as earlier noted. [0013] A first embodiment of the invention devised to meet the noted parameters for the improved, controlled recrystallization process comprises introducing the monomer solution at a temperature sufficient to ensure complete dissolution of the monomer, e.g., about 95.degree. C., intermittently and with substantial agitation into a quenching fluid having a maximum temperature at least about 35.degree. C. below the nominal monomer recrystallization temperature. For this purpose, the monomer solution is introduced into a quenching fluid having a base temperature preferably about 50.degree. C. below the nominal recrystallization temperature in such portions as to ensure that the temperature of the quenching mixture of quenching fluid and monomer solution is not increased above the upper limit of the preferred temperature range. Contemporaneous external cooling of the quenching mixture enables the lower range temperature to be recovered rapidly between periods of monomer solution introduction and ensures that the noted parameters are readily satisfied. The extent of such contemporaneous cooling may be utilized to establish the frequency and volume of the monomer solution introductions. [0014] In a second embodiment, the monomer solution may be introduced continuously, normally with substantial agitation, into the miscible quenching fluid at a rate, dependent upon the volume of the quenching fluid and the extent of contemporaneous cooling, which will maintain the specified quenching temperature range. In yet another embodiment, the quenching fluid and monomer solution may be continuously introduced contemporaneously into a mixing site, e.g., an externally cooled vessel or a conduit leading directly to filtration or other recrystallized monomer compound recovery apparatus, at such respective rates as will maintain the noted recrystallization temperature range. Such an in-line process thus enables continuous recovery of recrystallized monomer, if desired. BRIEF DESCRIPTION OF THE DRAWING [0015] The present invention will be described with reference to the accompanying drawing of which: [0016] FIG. 1 depicts the quenching temperature profile of an implementation of a first embodiment of the invention; [0017] FIG. 2 depicts the quenching temperature profile of another implementation of a first embodiment of the invention; [0018] FIG. 3 depicts the quenching temperature profile of yet another implementation of a first embodiment of the invention; [0019] FIG. 4 depicts the quenching temperature profile of an implementation of a second embodiment of the invention; [0020] FIG. 5 depicts the quenching temperature profile of another implementation of a second embodiment of the invention; [0021] FIG. 6 depicts the quenching temperature profile of yet another implementation of a second embodiment of the invention; Continue reading... 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